Math  /  Trigonometry

QuestionGiven cosθ=338\cos \theta=\frac{3 \sqrt{3}}{8}, what is sinθ\sin \theta ? sinθ=[?]\sin \theta=\frac{\sqrt{[?]}}{}

Studdy Solution

STEP 1

1. We are given cosθ=338\cos \theta = \frac{3 \sqrt{3}}{8}.
2. We need to find sinθ\sin \theta using the Pythagorean identity.
3. The Pythagorean identity states that sin2θ+cos2θ=1\sin^2 \theta + \cos^2 \theta = 1.

STEP 2

1. Use the Pythagorean identity to find sin2θ\sin^2 \theta.
2. Solve for sinθ\sin \theta.

STEP 3

Start with the Pythagorean identity:
sin2θ+cos2θ=1\sin^2 \theta + \cos^2 \theta = 1
Substitute the given value of cosθ\cos \theta into the equation:
sin2θ+(338)2=1\sin^2 \theta + \left(\frac{3 \sqrt{3}}{8}\right)^2 = 1

STEP 4

Calculate (338)2\left(\frac{3 \sqrt{3}}{8}\right)^2:
(338)2=(33)282=9×364=2764\left(\frac{3 \sqrt{3}}{8}\right)^2 = \frac{(3 \sqrt{3})^2}{8^2} = \frac{9 \times 3}{64} = \frac{27}{64}
Substitute back into the equation:
sin2θ+2764=1\sin^2 \theta + \frac{27}{64} = 1

STEP 5

Solve for sin2θ\sin^2 \theta:
sin2θ=12764\sin^2 \theta = 1 - \frac{27}{64}
Convert 1 to a fraction with a denominator of 64:
1=64641 = \frac{64}{64}
Subtract the fractions:
sin2θ=64642764=3764\sin^2 \theta = \frac{64}{64} - \frac{27}{64} = \frac{37}{64}

STEP 6

Take the square root of both sides to find sinθ\sin \theta:
sinθ=±3764\sin \theta = \pm \sqrt{\frac{37}{64}}
Simplify the square root:
sinθ=±378\sin \theta = \pm \frac{\sqrt{37}}{8}
The value of sinθ\sin \theta is:
sinθ=±378\sin \theta = \pm \frac{\sqrt{37}}{8}

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